Bypass dart and assembly

ABSTRACT

Embodiments of an improved bypass dart and assembly are described. In an embodiment, the plunger assembly includes a plunger having a first and second end. The plunger assembly may also include a cage attached to the second end of the plunger. Additionally, the plunger assembly may include a dart disposed within said cage. Further, the assembly may include an actuator coupled to the dart, the actuator configured to actuate the dart from a first position to a second position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This disclosure is a continuation-in-part of U.S. patent application Ser. No. 14/570,269 entitled “Improved Bypass Dart and Assembly,” filed on 15 Dec. 2014, which is incorporated herein in its entirety.

FIELD

This disclosure relates generally to oil and gas well systems, and more specifically, to an improved bypass dart and assembly.

BACKGROUND

It is well known that production from oil and gas wells can suffer due to the build-up of fluids at the bottom of the well. See e.g., U.S. Pat. No. 6,148,923, which is incorporated herein by reference. Various methods and devices have been developed to remove those fluids so as to improve the well's productivity.

One such device is known as a plunger, of which there are many variants known to those skilled in the art. For example, an auto-cycling plunger operates as follows: (1) it is dropped into the well (at the well's surface), (2) it free-falls down the well until it stops upon impact with the bottom of the well, and (3) it thereafter is caused (by pressure in the well) to travel back toward the surface of the well, pushing a “load” of liquid above it for removal at the well's surface. The plunger then is allowed to repeat that cycle, thereby ultimately removing enough fluid from the well to improve its production.

A number of problems have arisen from the use of prior art plungers. For example, due to the typically great distance between the surface and bottom of a well, the plunger travels at a great rate of speed when—due to its free-fall—it reaches and strikes the bottom of the well. Impacts between the plunger and the bottom of the well can be violent; they often are so violent that damage occurs (either immediately or over time due to repeated use) to either the plunger and/or whatever it strikes at the bottom of the well. As another example, the repeated cycling of the plunger causes at least certain of its parts eventually to wear out.

Damage to plungers due to impact and/or wear are prevalent in prior art “dart” bypass plungers. A “dart” bypass plunger is a well-known plunger that operates by free-falling down a well when its dart is in its open position, i.e., the dart is not seated so as to plug the otherwise hollow central passage of the plunger. This allows for the plunger to fall at a faster rate and can eliminate the need to stop the flow of the well during the decent. When the plunger strikes the bottom of the well, the dart is forced upward into a seated position in the bottom portion of the plunger, so that the top of the dart plugs or otherwise blocks gas or fluids from passing up through the hollow center of the plunger. This blocking action performed by the dart causes pressure to build up below the plunger, eventually lifting the plunger and an amount of liquid above it to the surface of the well, where the liquid is removed and the dart is forced out of its sealed position in the plunger (usually by a metal rod in the well's lubricator), thereby causing the plunger to free-fall back down the well to start another cycle.

While the operation of dart bypass plungers is well known to those skilled in the art, it is similarly well-recognized that the dart employed by such plungers cannot be allowed to freely move between its open and closed position in the plunger since if that were the case the dart would: (1) prematurely move to its closed position as the plunger free-falls down the well, or first strikes enough liquid or upwardly flowing gas to cause it to close; or (2) prematurely move to its open position (due to gravity or the force applied by liquid above it) as the plunger rises in the well. Either instance will cause the plunger to malfunction or at least operate less efficiently. Accordingly, several prior art techniques have been used to restrict the otherwise free movement of the dart between its open and closed position in the plunger.

One technique for restricting movement of the dart between its open and closed position is placing two or more metal plates around the outside of the dart, where friction between the metal plates and the dart is applied by wrapping one or more flexible O-rings around the metal plates (see e.g., U.S. Pat. No. 7,438,125). The flexibility in the O-rings is designed to impart enough friction between the metal plates and the outside surface of the dart that the dart is held in its desired open or closed position until the plunger reaches the top of the well (where the lubricator forces the dart from its closed to its open position) or reaches the bottom of the well (where the impact between the dart and the bottom of the well forces the dart from its open to its closed position). This technique has proven unsatisfactory to the inventors of the present invention at least because the metal plates wear, creating a larger inside diameter, so that the same O-ring compression applies less resistance on the dart, and thereby creating insufficient force to keep the dart in position.

Another technique for restricting movement of the dart between its open and closed position is by employing a clutch (around the dart) comprised of one or more c-clips disposed in the body of the plunger's cage housing the dart, so that the clutch engages the outside surface of the dart. While the c-clips apply friction to the dart that restricts its movement similar to the metal plates described above, this technique has proven unsatisfactory to the inventors of the present invention at least because the constant force applied by the dart to the c-clips causes the c-clips to were out too rapidly. Further, because the c-clips typically cannot be replaced without damaging the plunger, the useful life of the plunger itself can be limited by the life of the c-clips.

As indicated above, still other defects (or limitations) in prior art dart bypass plungers relates to damage imparted to them by their repeated collisions with the top and the bottom of the well. These collisions typically first cause failures at the weakest part(s) of the plunger and often at locations on the plunger closest to such collisions. For example, as is well known by those skilled in the art, prior art dart bypass plungers often have a cage at the bottom of the plunger for housing the dart. Such cages typically are attached to the plunger by a threaded connection. The cage also typically has a threaded cap at its end opposite the threaded connection to the plunger. When the plunger strikes the bottom of the well, these threaded connections—and especially the threaded connection at the cap, which is closest to the plunger's point of impact with the bottom of the well—typically are the first to fail as a result of the repeated impacts and, thereby, prematurely end the useful life of the plunger.

Finally, different working environments impart still other limitations on prior art dart bypass plungers. For example, environments that are sandy or otherwise corrosive can cause premature failure of the plunger at least through (1) the abrasiveness imparted by sand particles causing premature wear of the clutch/O-ring (i.e., the mechanism that keeps the dart in its open or closed position), and/or (2) the clogging of the passageways so much that the dart no longer appropriately slides between its open and closed position.

SUMMARY

Embodiments of apparatuses and systems having an improved bypass dart and assembly are described. In an embodiment the apparatus comprises a plunger assembly. The plunger assembly may include a plunger having a first and second end, a cage attached to the second end of the plunger, a dart disposed within said cage having a body with at least two surfaces, where a first surface is a raised surface relative to a second surface, and an actuator disposed at least partially within the plunger, the actuator configured to actuate the dart from a first position to a second position.

DETAILED DESCRIPTION

The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein.

FIG. 1 is a schematic diagram illustrating one embodiment of a system having a well plunger.

FIG. 2 is a schematic diagram illustrating one embodiment of a system having a well plunger.

FIG. 3 is an assembly diagram of one embodiment of a dart bypass plunger.

FIG. 4 is a cross-sectional diagram of one embodiment of a dart bypass plunger.

FIG. 5 is an assembly diagram of one embodiment of a dart for a dart bypass plunger.

FIG. 6 is an assembly diagram of another embodiment of a dart for a dart bypass plunger.

FIG. 7 is a cross-sectional diagram of one embodiment of a dart for a dart bypass plunger.

FIG. 8 is a cross-sectional diagram of one embodiment of a dart bypass plunger.

FIG. 9 is a cross-sectional diagram of one embodiment of the cage and dart portion of a dart bypass plunger.

FIG. 10 is a cross-sectional diagram of one embodiment of a dart bypass plunger.

FIG. 11 is a cross-sectional diagram of one embodiment of the cage and dart portion of a dart bypass plunger.

FIG. 12 is a perspective view diagram illustrating one embodiment of a dart bypass plunger with enclosed rod.

FIG. 13 is an end view diagram illustrating one embodiment of a dart bypass plunger with enclosed rod.

FIG. 14 is an end view diagram illustrating one embodiment of a dart bypass plunger with enclosed rod.

FIG. 15A is a side view diagram illustrating one embodiment of a dart bypass plunger with enclosed rod.

FIG. 15B is a cross-section view diagram illustrating one embodiment of a dart bypass plunger with enclosed rod.

DETAILED DESCRIPTION

Various features and advantageous details are explained more fully with reference to the nonlimiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known starting materials, processing techniques, components, and equipment are omitted so as not to unnecessarily obscure the invention in detail. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments of the invention, are given by way of illustration only, and not by way of limitation. Various substitutions, modifications, additions, and/or rearrangements within the spirit and/or scope of the underlying inventive concept will become apparent to those skilled in the art from this disclosure.

The present embodiments include a well system for oil and/or gas production. In an embodiment, the well system includes a well assembly comprising a well bottom, a wellhead, and a well pipe coupling the wellhead to the well bottom. The system may also include a plunger lift assembly configured to lift fluid from the well bottom to the wellhead. In an embodiment, the system includes a bumper assembly disposed proximate to the well bottom and configure to catch the plunger lift assembly before reaching the well bottom. The system may also include a lubricator disposed proximate to the wellhead.

In an embodiment, the lubricator may include a main body configured to receive fluid raised by the plunger lift assembly from the well assembly, a port in the main body configured to conduct fluid as it is received by the main body. The main body and the port may be a unitary structure devoid of applied junctions. As used herein, the term “unitary structure” means a single piece or part. As used herein, the term “applied junction” means the union of separate components applied together by a secondary process. For example, a port applied to a main body by an applied junction would include a port, coupler, or connector welded, bolted, adhesively applied, or otherwise applied to the main body in a step that is secondary to initial formation of the main body. For example, a lubricator structure that is forged with integrated ports is devoid of applied junctions in some embodiments.

FIG. 1 is a schematic diagram illustrating one embodiment of a system 100 having a well plunger. In the depicted embodiment, the system 100 includes a well assembly having a well bottom 106 and a wellhead 104 coupled together by well pipe 108. The well pipe 108 may be inserted into a hole formed by the well casing 110. Well casing 110 may be formed in the ground 112 with concrete or other structurally adequate materials. The well pipe 108 and well casing 110 may be of varying length depending on the depth of the well. In some embodiments, the well may be a vertical well as shown. In other embodiments, the well may be a horizontal well configuration, or a hybrid well configuration, as will be recognized by one of ordinary skill in the art.

The system 100 may include a bumper assembly 114 proximate to the well bottom 106. In an embodiment, the plunger 116 may be configured to lift fluid 120 from the well bottom 106 to the wellhead 104. The fluid 120 is received by the lubricator 102 and expelled through one or more ports to peripheral components (not shown). In an embodiment, the plunger 116 may engage with a stopper, such as ball 118. In some embodiments, the ball 118 may be a steel sphere configured to be received by a portion of the plunger 116. The stopper may restrict flow of fluid through and/or around the plunger 116, thereby causing the plunger to rise toward the lubricator 102. The lubricator 102 may cause the stopper 118 to be released, thereby allowing the passage of fluids through and/or around the plunger 116, and thereby causing the plunger 116 to fall back toward the bumper 114. The bumper 114 may dampen the impact forces when the plunger 116 approaches the bottom of the well 106. At that point, the stopper 118 may be received by the plunger 116 again, and the process may repeat, thereby cyclically lifting fluid 120 to be expelled by the lubricator 102.

FIG. 2 is a schematic diagram illustrating one embodiment of a system 200 having a well plunger. As in the embodiment of FIG. 1, the well may include a well bottom 106 and a wellhead 104 separated by a well pipe 108 and a well casing 110 formed in the ground 112. In the depicted embodiment, the lubricator 102 may include a main body 202. The lubricator 102 may also include a plurality of fluid conduit ports 204 a-b, and plurality of instrumentation port(s) 210 a. In addition, the lubricator 102 may include a catcher port 210 b configured to receive a catch assembly (not shown) for catching and releasing the plunger 218 within the lubricator 102. Additionally, the lubricator 102 may include an inlet port 206 having an inlet flange 208 for coupling the lubricator 102 to the wellhead 104.

In an embodiment, the system may include a caged dart plunger 218 having an internally captured dart 220 as a sealing member, which functionally replaces the ball 118 of FIG. 1. An example of a caged dart plunger 218 is described in greater detail in U.S. patent application Ser. No. 14/570,269 entitled “Improved Bypass Dart and Assembly,” filed on Dec. 15, 2014, which is incorporated herein in its entirety. Although the caged dart plunger is one embodiment of a plunger assembly that may be suitable for use according to the present embodiments, one of ordinary skill will recognize alternative embodiments that may be equally suitable, including for example, the ball stopper embodiment described in FIG. 1.

In an embodiment, the progressive rate bumper 222 may include a progressive rate spring 224. One example of a progressive rate bumper 222 that may be suitable for use with the present embodiments is described in U.S. patent application Ser. No. 14/333,058 entitled “Bumper Assembly Having Progressive Rate Spring,” filed on Jul. 16, 2014, which is incorporated herein by reference in its entirety. Although the progressive rate bumper 224 is one embodiment of a bumper 114 that may be included with the present embodiments, one of ordinary skill will recognize alternative embodiments of bumpers 114 which may be equally suitable depending on the use conditions.

In the embodiment, of FIG. 2, the lubricator 102 may include a spring assembly 214, which may further include a catch spring 216 disposed in a spring housing 212. In an embodiment, the catch spring 216 may also be a progressive rate spring, as described in relation to the bumper spring assembly. Alternatively, the catch spring 216 may be a constant rate spring. One of ordinary skill will recognize various embodiments of a spring/catch assembly that may be used in conjunction with the present embodiments of the lubricator 102 depending on the use conditions. The spring assembly 214 may work in conjunction with the catch assembly (not shown), which is received by the catch port 210 b. The catch assembly may include a flange or lever for locking the plunger 218 in place, or for releasing the plunger 218 back into the well.

FIG. 3 illustrates an exemplary embodiment of the present invention. FIG. 3 shows dart bypass plunger 300, consisting generally of plunger body 310 and cage 320. FIG. 4 depicts a cross-section of dart bypass plunger 300.

As best shown by FIG. 4, the plunger has a generally hollow interior 400 so that liquid and/or gas can flow there-through when the plunger is deployed in a well. FIG. 4 also shows cage 410 (in threaded engagement with the plunger body near the bottom portion thereof) housing dart 420. In this embodiment, cage 410 is unitary in nature in that, while it is attached to the plunger body using threads, it has no other separate piece or component attached thereto using threads.

As shown, dart 420 is slidably mounted in cage 410 so that it can be positioned in at least an open or closed position relative to the bottom opening of the plunger. For example, the dart's open position exists when dart 420 is positioned so as to allow gas or liquid to flow substantially freely through the generally hollow interior 400 of the plunger when the device is deployed in a well. The dart's closed position exists when dart 420 is positioned so as to retard gas or liquid from freely flowing through the generally hollow interior 400 of the plunger. (Note, in this embodiment, the upper surface of the dart is machined to snuggly mate with the lower opening of the plunger body so that more pressure builds below the plunger when the dart is in its closed position than when the dart is in its open position.)

As further depicted by FIG. 4, cage 410 employs clutch 430 to retard movement of dart 420 between its open and closed position. Clutch 430 can be any mechanism known to those skilled in the art for retarding the movement of dart 420, preferably including either one or more c-clips and/or one or more O-rings. In other words, the friction imparted by clutch 430 on the outside surface(s) of dart 420 keeps dart 420 from freely sliding between its open and closed position. This is important because, as described above, proper (or efficient) operation of plunger 300 requires that dart 420 generally remain in its open position as the plunger free-falls down the well, and that dart 420 generally remain in its closed position as the plunger rises in the well. Clutch 430 also should be tuned (in terms of the amount of force it exerts on dart 420) so that dart 420 generally remains in its open or closed position as the plunger travels down or up the well, respectively, but also so that it is able to be moved from its closed to its open position when the plunger reaches the surface of the well, and moved from is open to its closed position when the plunger reaches the bottom of the well.

An exemplary embodiment of dart 420 is more specifically depicted by FIG. 5. As shown, dart 420 comprises upper end 500 and lower end 510. Disposed between upper end 500 and lower end 510 is body 520. In this exemplary embodiment, body 520 is sized to have at least one surface raised relative to its surrounding or adjacent surface(s). For example, in the circumstance/embodiment where a cross-section of body 520 is circular, the diameter of the raised surface is greater than the diameter of its surrounding or adjacent surface(s). In this embodiment, and as described in more detail below, the effect of the raised surface impacts the life of clutch 430 and, therefore, the life of the dart bypass plunger itself.

Specifically, in this particular embodiment, the raised and lower surfaces of body 520 for dart 420 have the effect of (1) exerting less force on clutch 430 when clutch 430 is engaged with a lower surface of body 520 and (2) exerting more force on clutch 430 when clutch 430 is engaged with a raised surface of body 520. Put another way, due to the engagement between clutch 430 and body 520, clutch 430 exerts more force on the raised surface of body 520 than it does on the lower surface of body 520.

Still further, in this embodiment, the raised and lower surfaces of body 520 are positioned relative to one another so that clutch 430 effectively applies less force to body 520 when dart 420 is in its open and/or closed position. In other words, clutch 430 will be positioned relative to a lower surface of body 520 when dart 420 is open and/or closed. The longer clutch 430 is exerting less force on body 520 than it is otherwise capable of exerting, the longer clutch 430 will continue to effectively operate before it wears out. And, since dart 420 is in its open or closed position (thereby reducing the force clutch 430 exerts on body 520) more often than it is between such positions (thereby increasing the force clutch 430 exerts on body 520), the longer this design will enable clutch 430 to last before wearing out.

FIG. 6 depicts another exemplary embodiment of a dart, this one shown as dart 600. As shown, dart 600 includes upper end 500 and lower end 510. Disposed between upper end 500 and lower end 510 is the body of dart 600. In this embodiment, the body comprises two separate raised surfaces, 610 and 620 respectively. These raised surfaces function similar to the one raised surface in FIG. 5. Specifically, as shown in FIGS. 8 and 9 and described below, raised surface 620 operates (in conjunction with clutch 430) to hold dart 600 in its closed position. Likewise, as shown in FIGS. 10 and 11 and described below, raised surface 610 operates (in conjunction with clutch 430) to hold dart 600 in its open position. Raised surfaces 610 and 620 preferably, but need not, have the same outside diameters.

As it was with respect to the one raised surface in FIG. 5, the two raised surfaces 610 and 620 in FIG. 6 (relative to their adjacent surfaces) have the effect of reducing the amount of strain placed on clutch 430 when dart 600 is in its open and closed positions. Moreover, the reduced diameter of dart 600 between raised surfaces 610 and 620 has the further benefit of prolonging the life of clutch 430 by (1) reducing the strain placed on the clutch as the dart transitions between its open and closed positions and (2) reducing the abrasive force that contaminants on the dart impart to the clutch during such transitions, which can unduly wear the clutch, especially if an O-ring is employed as the clutch mechanism.

Since clutch wear often is a limiting factor in the life of an auto-cycling plunger, the above-described designs prolong the life of the plunger, thereby saving equipment costs and well down-time (to replace the plunger) and collectively improve the efficiency of operating the well itself.

FIG. 7 depicts yet another embodiment of the dart for a dart bypass plunger. While FIG. 7 shows dart 700 having two raised surfaces between upper end 500 and lower end 510 (as shown in FIG. 6), it need not include them, or any raised surface for that matter. The embodiment of FIG. 7 does, however, include channel 710 that runs from lower end 510 toward upper end 500. At the upper portion of channel 710, diversion channels 720 and 730 exit on opposite sides of the dart. While two diversion channels are shown, less or more are possible and are within the scope of the present invention. Likewise, while not shown in FIG. 7, one or more other diversion channels are preferably formed as pathways from channel 710 to the exterior of the dart. These other channels are depicted as channel 740 in FIGS. 8-11. Channel 740 is preferably, but not necessarily, offset by 90 degrees from channels 720 and 730. In this manner, flow of the well (whether it be gas or liquid) is able to travel into channel 710 at its opening in the lower end 510 of the dart and exit one or more of the diversion channels 720, 730, and/or 740.

FIGS. 8 and 9 show yet another exemplary embodiment of the present invention. In this embodiment, the lower end of the dart has a reduced outside diameter to provide a gap or space between the outside, lower end of the dart and the inside diameter of cage 410. This reduced outside diameter also is depicted in FIG. 6 at the portion of the dart below raised surface 620. While FIGS. 8 and 9 show the dart depicted in FIG. 7, any dart will suffice so long as its lower end has a reduced outside diameter that provides a gap (or space) between the outside, lower end of the dart and the inside diameter of cage 410. The amount of space between the outside, lower end of the dart and the inside diameter of cage 410 should be sufficient to allow gas or liquid to flow through that space and out port 810 in cage 410. While FIG. 8 shows only one port 810, a preferred embodiment of the invention includes three such ports, each offset from one another by 120 degrees. This flow operates to cleanse debris that might otherwise become lodged between the dart and the cage and that would, as a result, detrimentally restrict the dart from sliding between its open and closed positions and also unduly wear clutch 430, especially if an O-ring is deployed as the clutch mechanism.

In yet another embodiment of the present invention, channels 710, 720, 730, and 740 operate to create passageways through which gas and/or liquids flow. Specifically, as the dart bypass plunger travels up or down the well, gas and/or liquids travel into channel 710 at the lower end of the dart and exit the dart through channels 720, 730, and/or 740. The turbulent nature of the exiting gas/liquids acts to cleanse or otherwise dislodge contaminants from the outside surface of the dart and from the interface between the dart and its cage. The beneficial effects of this turbulent flow are similar to those described above for the flow that takes place in the space between the outside, lower end of the dart and the inside diameter of cage 410.

FIG. 12 is a perspective view diagram illustrating one embodiment of a dart bypass plunger 218 with enclosed rod 1212. In an embodiment, the enclosed rod 1212 may be configured to actuate the dart 420 within the cage 410. The rod 1212 may be captured within the plunger body 310. In one such embodiment, the plunger body 310 may include one or more turbulence control features 1202 for controlling a fall rate or rise rate of the plunger 218 within the well. Additionally, the plunger 218 may include rifling grooves 1204 configured to cause the plunger to rotate within the well pipe 108. Rotation of the plunger 218 may cause more even wear of the plunger, particularly when the plunger is deployed in a deviated well system.

In an embodiment, the plunger 218 may further comprise a first set of passages 1208 disposed on a first end of the plunger 218 and a second set of passages 1210 disposed on a second end of the plunger 218. The first set of passages 1208 and the second set of passages 1210 may be connected by the hollow interior 400 of the plunger 218. Further, port 1206 may allow passage of fluid into the hollow interior 400 for clearing debris from the hollow interior 400.

The plunger 218 may additionally include a dart 420 disposed within a cage 410. As explained above, the dart may transition between an open and closed position within the cage, thereby allowing fluid to flow between the first set of passages 1208 and the second set of passages 1210, or blocking passage of fluid between the first set of passages 1208 and the second set of passage 1210. In a further embodiment, transitions between the dart's closed and open position may be effectuated by the rod 1212 captured within the main body 310.

FIG. 13 is an end view diagram illustrating one embodiment of a dart bypass plunger 218 with enclosed rod 1212. In an embodiment, the end depicted in FIG. 13 may be oriented toward the well bottom 106. The first set of passages 1208 may be disposed within the body 310. In one embodiment, the passages 1208 may be evenly distributed at 90 degrees around the central axis of the plunger 218. Further, rod 1212 may be captured by at least a portion of the body 310.

FIG. 14 is an end view diagram illustrating one embodiment of a dart bypass plunger 218 with enclosed rod 1212. In an embodiment, the end of FIG. 14 may be oriented toward the wellhead 104. In such an embodiment, the second set of passages 1210 may be disposed within either the body 310 or the cage 410. In an embodiment the second set of passages 1210 may be evenly distributed at 120 degrees around the central axis of the plunger 218. One of ordinary skill will recognize that alternative orientations may be used, depending upon the configuration of the dart and well assembly.

FIG. 15A is a side view diagram illustrating one embodiment of a dart bypass plunger 218 with enclosed rod 1212. FIG. 15B is a cross-section view diagram illustrating one embodiment of a dart bypass plunger 218 with enclosed rod 1212, wherein the section is taken along the central axis of the plunger 218. As shown, rod 1212 is slidably mounted in plunger 218 and held in alignment by its seated engagement at the upper and lower ends of the plunger 218. The rod 1212 may include one or more grooves 1502 configured to allow passage of fluid and/or debris around the outer diameter of the rod 1212, thereby preventing debris from jamming or otherwise restricting the slidable nature of rod 1212 within plunger 218.

As explained above, the rod 1212 is designed to displace dart 420 from its closed position (see FIGS. 8-9) when the plunger rises to the top of the well and the rod 1212 strikes a stopper mechanism in lubricator 102. More specifically, after the rod 1212 strikes the stopper mechanism, the upward momentum of the plunger (aided by pressure in the well) continues to drive the plunger against the stopper, thereby driving rod 1212 (by virtue of its slidable mount in the plunger) down through the plunger and forcing dart 420 (against the force exerted by clutch 430) into its open position.

FIG. 15B shows a preferred embodiment in which the top of dart 420 includes a receiver area 1504 for receiving the bottom end of rod 1212. Alternate embodiments are possible. For example, the dart 420 need not include receiver area 1504, so that in that embodiment rod 1212 would simply strike the top surface of dart 420 to force the dart from its closed position to its opened position. While not shown in FIG. 15B, rod 1212 preferably includes a shelf positioned on the upper end of the rod (but below its slidable engagement with the upper portion of plunger 218) in order to: (1) keep rod 1212 from sliding out the top end of plunger 218, and (2) position rod 1212 so that it engages with the top end of dart 420 when dart 420 is in its closed position and rod 1212 is in its upper-most, slidable position.

Finally, when in operation and the plunger reaches the bottom of the well, dart 420 will strike bumper assembly 114, thereby driving dart 420 into its closed position and (consequently) rod 1212 upward into an elongated position (relative to its position when dart 420 is in its open position) and ready to strike the stopper in lubricator 102 to repeat the process.

Although the invention(s) is/are described herein with reference to specific embodiments, various modifications and changes can be made without departing from the scope of the present invention(s), as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present invention(s). Any benefits, advantages, or solutions to problems that are described herein with regard to specific embodiments are not intended to be construed as a critical, required, or essential feature or element of any or all the claims.

Unless stated otherwise, terms such as “first” and “second” are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements. The terms “coupled” or “operably coupled” are defined as connected, although not necessarily directly, and not necessarily mechanically. The terms “a” and “an” are defined as one or more unless stated otherwise. The terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include” (and any form of include, such as “includes” and “including”) and “contain” (and any form of contain, such as “contains” and “containing”) are open-ended linking verbs. As a result, a system, device, or apparatus that “comprises,” “has,” “includes” or “contains” one or more elements possesses those one or more elements but is not limited to possessing only those one or more elements. Similarly, a method or process that “comprises,” “has,” “includes” or “contains” one or more operations possesses those one or more operations but is not limited to possessing only those one or more operations. 

1. A plunger assembly, comprising: (a) a plunger having a first and second end; (b) a cage attached to the second end of the plunger; (c) a dart disposed within said cage having a body with at least two surfaces, where a first surface is a raised surface relative to a second surface; and (d) an actuator disposed at least partially within the plunger, the actuator configured to actuate the dart from a first position to a second position.
 2. The plunger assembly of claim 1, wherein the dart is slidably mounted in the cage so that the dart can be positioned in at least an open or closed position relative to the second end of the plunger.
 3. The plunger assembly of claim 2, wherein the cage includes a clutch to retard movement of the dart between its open and its closed position.
 4. The plunger assembly of claim 3, wherein the dart comprises a receiver portion, the receiver portion configured to receive at least a portion of the actuator.
 5. The plunger assembly of claim 1, wherein the actuator further comprises a rod disposed along a longitudinal axis of the plunger assembly.
 6. The plunger assembly of claim 5, wherein the rod further comprises a feature configured for passage of fluid and debris along a surface of the rod.
 7. The plunger assembly of claim 5, wherein a portion of the rod protrudes from the first end of the plunger.
 8. The plunger assembly of claim 5, wherein a portion of the rod is configured to engage a receiver portion of the dart.
 9. The plunger assembly of claim 3, wherein the body of the dart is disposed between an upper end of the dart and a lower end of the dart.
 10. The plunger assembly of claim 9, wherein the clutch exerts more force on the raised surface of the body of the dart than it does on the lower surface of the body of the dart.
 11. The plunger assembly of claim 10, wherein the raised and lower surfaces of the body of the dart are positioned relative to one another so that the clutch exerts less force on the body of the dart when the dart is in its open and/or closed position.
 12. The plunger assembly of claim 11, wherein the body of the dart has a circular cross-section and the diameter of the raised surface is greater than the diameter of the lower surface.
 13. The plunger assembly of claim 12, wherein the clutch comprises one or more c-clips.
 14. The plunger assembly of claim 12, wherein the clutch comprises one or more O-rings.
 15. The plunger assembly of claim 14, wherein the cage includes only one set of threads, which connect the cage to the second end of the plunger.
 16. A plunger assembly, comprising: (a) a plunger having a first and second end; (b) a cage attached to the second end of the plunger; (c) a dart disposed within said cage having a body with at least three surfaces, where two surfaces are raised surfaces relative to the third, lower surface; and (d) an actuator disposed at least partially within the plunger, the actuator configured to actuate the dart from a first position to a second position.
 17. The plunger assembly of claim 16, wherein the cage includes at least one channel that allows gases or liquids to pass from inside the cage to outside the cage.
 18. The plunger assembly of claim 17, further comprising a gap between a lower end of the dart and a lower end of the cage that allows gases or liquids to flow through the gap and out the at least one channel in the cage.
 19. A dart assembly for a plunger device, the dart assembly comprising: (a) a dart body having a first end and a second end; and (b) an actuator configured to actuate the dart from a first position to a second position. (c) wherein the first end is configured to protrude from an opening in a cage assembly, the cage assembly configured to retain the dart body within a plunger assembly, and the second end is configured to receive the actuator.
 20. The dart assembly of claim 19, wherein the dart comprises a receiver portion, the receiver portion configured to receive at least a portion of the actuator; and wherein a portion of the rod is configured to engage the receiver portion of the dart. 